• What: a narrow, funnel shaped column of
spiral winds that extend downward from
the cloud base and touches the ground.
=360-500 kilometers per hour
• When: Spring or summer day. Air is very
moist. Thunderstorms are approaching;
air is forced to rise rapidly.
• Why: low air pressure causes the air to
expand and cool, it cools to the dew point
to form a cloud.
• Where: Mississippi
River Valley and the
Great Plains. Warm
moist air from the
Gulf, cool air from the